Method and apparatus for heat-sealing container

ABSTRACT

A heat welding member  23  of a seal head  21  formed in the shape of a flange portion  11   a  of a container  10  is heated by high frequency induction heating and a cap  12  is welded by pressing the heated seal head  21.  By using the seal head  21  comprising the heat welding member  23  having a shape necessary for sealing the cap  12,  influences by temperature drop and inflation of gas in a head space can be prevented and sealing at a high speed and in a stable manner can be achieved.

TECHNICAL FIELD

This invention relates to a method and an apparatus for heat-sealing acontainer and, more particularly, to a method and an apparatus capableof carrying out heat-heating at a high speed and in a stable manner in acase where a cap in the form of a film should be heat-sealed to acontainer main body made of paper or synthetic resin and formed in theshape of a cup.

BACKGROUND ART

A container in which a cap in the form of a film is heat-sealed on acontainer main body made of paper or synthetic resin and formed in theshape of a cup is used broadly as a container for food etc., as, forexample, a container for jelly, baby food, viscous food such as soup ormiso or cooked food.

For sealing a container main body and a cap in such a container,heat-sealing which carries out sealing by heating using a seal head isgenerally used.

As such heat-sealing method, Japanese Patent Application Laid-openPublication No. 2004-250027 discloses a method in which a cap isconveyed and placed on a container by cap pressing and conveying meansdisposed above container conveying means and, while the state in whichthe cap is in close contact with the container is maintained, inductionheating is carried out by a high frequency seal head which is disposedabove the cap without contacting the cap. According to this method,sealing can be achieved at a high speed without vertically moving theseal head or container.

Japanese Patent Application Laid-open Publication No. 11-20801 discloseshigh speed adhesion between a cap and a container by using of bothheating with a heater cartridge and high frequency induction heating orsupersonic vibration heating.

Japanese Patent Application Laid-open Publication No. 58-19536 disclosesthat, as shown in its FIG. 4, a pressing and heating belt 4 in which ametal member 2 is sandwiched between a heat resisting member 3 isprovided above a container conveying belt conveyer 1 in a manner to movesynchronously in parallel with the conveyer 1 and that a high frequencyinduction heating coil 5 is disposed in the belt 4 to high frequencyinduction heating the pressing and heating belt 4 so that a cap 7 placedon a container 6 may be sealed.

SUMMARY OF THE INVENTION

In carrying out sealing at a high speed by using one of the abovedescribed heat-sealing methods, if capacity of a heat receiving andimparting portion of a seal head, i.e., heat capacity, is small,temperature of the seal head tends to drop during sealing when the sealhead is pressed against the cap and heating of the cap is made in aperipheral portion of the cap and, therefore, a seal head having a moreor less lump shape and having a large heat capacity must be used.

If, however, one attempts to carry out sealing at a high speed by usinga large seal head, not only the peripheral portion of the cap but alsothe central portion of the cap tend to be heated and thereforetemperature of the central portion tends to rise and, as a result, gasin a head space of the container is inflated in a stage before thewelded portion is completely solidified and wrinkles are produced in thecap thereby causing difficulty in sealing.

Moreover, if one attempts to carry out sealing at a high speed i.e., ina short period of time, by elevating temperature of the seal head, thecap tends to adhere to the seal head thereby causing difficulty insealing and, in this case, limitation is posed on the type of materialwhich can be used as the cap.

Further, in the case of Japanese Patent Application Laid-openPublication No. 2004-250027 in which the cap is heated by high frequencyinduction heating, the cap must be heated directly and, therefore,sealing by heating can be made only in the case that the cap is made ofmetal.

Furthermore, in all of the above described methods, the entire surfaceof the cap is heated and, as a result, gas in the head space of thecontainer is inflated thereby causing difficulty in sealing.

The present invention has been made in view of these problems of theprior art methods. It is an object of the invention to provide a methodand an apparatus for heat-sealing a container capable of carrying outsealing at a high speed and in a stable manner regardless of material ofa cap.

For achieving the above described object of the present invention, inthe first aspect of the invention, there is provided a method forheat-sealing a container by sealing the container by heat welding a capon a flange portion provided in an opening portion of the containercomprising a step of high frequency induction heating a seal head formedin the shape of the flange portion of the container and pressing the capwith the heated seal head to weld the cap to the container.

According to this method for heat-sealing a container, since the sealhead formed in the shape of the flange portion of the container is highfrequency induction heated and the heated seal head is pressed on thecap to weld the cap, by using a seal head having a shape necessary forsealing the cap, influence by dropping in the temperature and inflationof gas in the head space can be prevented and sealing at a high speed ina stable manner can be achieved.

In the second aspect of the invention, there is provided a method forheat-sealing a container as defined in the first aspect furthercomprising a step of cooling the seal head while the heated seal head ispressing the cap.

According to this method for heat-sealing a container, the seal head iscooled while the heated seal head is pressing the cap. Since pressing isfinished after the seal head is cooled, even if sealing temperature israised, adhering of the cap to the seal head can be prevented andsealing at a high speed and in a stable manner can be achieved even in ahigher degree.

In the third aspect of the invention, there is provided a method forheat-sealing a container as defined in the second aspect wherein coolingof the seal head is made by supplying a cooling medium into the sealhead.

According to this method for heat-sealing a container, since cooling ofthe seal head is made by supplying a cooling medium into the seal head,cooling of the seal head can be made easily.

In the fourth aspect of the invention, there is provided a method forheat-sealing a container by sealing the container by heat welding a capon a flange portion provided in an opening portion of the container witha seal head comprising a heating ring formed along the shape of theflange portion and a high frequency induction heating coil provided onthe inside of the heating ring via magnetic shielding plates, saidmethod comprising a step of high frequency induction heating the heatingring with the high frequency induction heating coil and pressing the capwith the heating ring to weld the cap to the container.

According to this method for heat-sealing a container, the seal headwith which the cap is heat welded on the flange portion provided in theopening portion of the container comprises the heating ring formed alongthe shape of the flange portion and the high frequency induction heatingcoil provided on the inside of the heating ring via magnetic shieldingplates and the heating ring is high frequency induction heated with thishigh frequency induction heating coil and pressed on the cap to weld thecap. Therefore, by using a seal head having a heating ring having ashape necessary for sealing the cap and concentrically heating theheating ring shielded by the magnetic shielding plates, influence bydropping in the temperature and inflation of gas in the head space canbe prevented and sealing at a high speed in a stable manner can beachieved.

In the fifth aspect of the invention, there is provided a method forheat-treating a container as defined in the fourth aspect wherein supplyof electricity to the high frequency induction heating coil is stoppedafter the heating ring has been heated to a predetermined temperatureand then pressing with the heating ring is continued for a predeterminedperiod of time.

According to this method for heat-sealing a container, since supply ofelectricity to the high frequency induction heating coil is stoppedafter the heating ring has been heated to a predetermined temperatureand then pressing with the heating ring is continued for a predeterminedperiod of time, heating with the heating ring which has been heated to apredetermined temperature is continued for a predetermined period oftime necessary for heat welding and, therefore, sealing can be made in asealing state which becomes stable and proper in a short period of time.

In the sixth aspect of the invention, there is provided a method forheat-treating a container as defined in the fourth or fifth aspectwherein the heating ring is cooled while pressing with the heating ringis continued.

According to this method for heat-sealing of a container, since theheating ring is cooled while pressing with the heating ring iscontinued, even if the temperature is raised, pressing is finished afterthe heating ring is cooled and, therefore, adhering of the cap to theheating ring can be prevented and sealing at a high speed and in astable manner can be achieved even in a higher degree.

In the seventh aspect of the invention, there is provided a method forheat-sealing a container as defined in the sixth aspect wherein theheating ring has a hollow portion and cooling of the heating ring ismade by supplying a cooling medium into the hollow portion.

According to this method for heat-sealing a container, since the heatingring has a hollow portion and cooling of the heating ring is made bysupplying a cooling medium into the hollow portion, cooling of theheating ring at a high temperature can be made easily in a short periodof time.

In the eighth aspect of the invention, there is provided a method forheat-sealing a container as defined in the seventh aspect whereincooling of the heating ring with the cooling medium and supplying of thecooling medium are made by providing a plurality of cooling mediumsupplying and exhausting openings in the hollow portion of the heatingring and supplying and exhausting the cooling medium from a differentone of the supplying and exhausting openings in a predetermined order orat random.

According to this method for heat-sealing a container, cooling of theheating ring with the cooling medium and supplying of the cooling mediumare made by providing a plurality of cooling medium supplying andexhausting openings in the hollow portion of the heating ring andsupplying and exhausting the cooling medium from a different one of thesupplying and exhausting openings in a predetermined order or at random.By supplying and exhausting the cooling medium from a different one ofthe supplying and exhausting openings in a predetermined order or atrandom, the heating ring can be cooled to a uniform temperature wherebyheating temperature for next heating can be made uniform andheat-sealing can be made in a stable manner.

In the ninth aspect of the invention, there is provided an apparatus forheat-sealing a container comprising a seal head for sealing thecontainer by heat welding a cap on a flange portion provided in anopening portion of the container, said seal head comprising a seal headmain body, a heat welding member provided in the seal head main body andformed in the shape of the flange portion, and a high frequencyinduction heating coil provided in the seal head main body for highfrequency induction heating the heat welding member.

According to this apparatus for heat-sealing a container, since theapparatus comprises the heat welding member provided in the seal headmain body and formed in the shape of the flange portion, and the highfrequency induction heating coil provided in the seal head main body forhigh frequency induction heating the heat welding member, by heating theheat welding member in the form of the flange portion with the highfrequency induction heating coil, the heat welding member can be heatedto a necessary temperature for sealing in a short period of time and,therefore, influence of dropping in the temperature and inflation of gasin the head space can be prevented and high-speed and stable sealing canbe achieved with a seal head having a shape necessary for sealing of thecap.

In the tenth aspect of the invention, there is provided an apparatus forheat-sealing a container as defined in the ninth aspect wherein the heatwelding member comprises a cooling medium flow-path which enables theheat welding member to cool while pressing of the heat welding member onthe cap is maintained.

According to this apparatus for heat-sealing a container, since the heatwelding member comprises a cooling medium flow-path which enables theheat welding member to cool while pressing of the heat welding member onthe cap is maintained, cooling of the seal head can be made easily and,therefore, even if the temperature is raised, by finishing pressingafter the seal head is cooled, adhering of the cap to the seal head canbe prevented and sealing at a high speed and in a stable manner can beachieved even in a higher degree.

In the eleventh aspect of the invention, there is provided an apparatusfor heat-sealing a container as defined in the ninth or tenth aspectwherein the heat welding member comprises a non-welding member on asurface of the heat welding member which presses the cap.

According to this apparatus for heat-sealing a container, since the heatwelding member comprises a non-welding member on a surface of the heatwelding member which presses the cap, even if the sealing temperature israised, adhering of the cap to the seal head can be prevented bycovering of the seal head and sealing at a high speed and in a stablemanner can be achieved even in a higher degree.

In the twelfth aspect of the invention, there is provided an apparatusfor heat-sealing a container as defined in the tenth or eleventh aspectwherein the heat welding member comprises cooling medium exhaustingmeans for exhausting the cooling medium in the cooling medium flow-pathafter cooling of the cap.

According to this apparatus for heat-sealing a container, since the heatwelding member comprises cooling medium exhausting means for exhaustingthe cooling medium in the cooling medium flow-path after cooling of thecap, heating for sealing a next cap can be made in an even shorterperiod of time whereby sealing can be made at a high speed and in astable manner.

In the thirteenth aspect of the invention, there is provided anapparatus for heat-sealing a container as defined in any of theninth-twelfth aspects wherein the seal head main body comprisestemperature holding means for holding heating temperature of the heatwelding member.

According to this apparatus for heat-sealing a container, since the sealhead main body comprises temperature holding means for holding heatingtemperature of the heat welding member, a temperature which becomes abasis of temperature range of heating and cooling can be maintained and,therefore, when heating and cooling are repeated, sealing can be made ata high speed and in a stable manner in an even shorter period of time.

In the fourteenth aspect of the invention, there is provided anapparatus for heat-sealing a container comprising a seal head andsealing the container by heating the seal head and pressing a cap placedon a flange portion of an opening portion of the container with theheated seal head to heat-weld the cap to the container, said seal headcomprising a heating ring shaped along the shape of the flange portion,and a high frequency induction heating coil wound in a plurality ofwindings provided on the inside of the heating ring and held betweenmagnetic shielding plates.

According to this apparatus for heat-sealing a container, sinceapparatus for heat-sealing the container comprising the seal head andsealing the container by heating the seal head and pressing the capplaced on the flange portion of the opening portion of the containerwith the heated seal head to heat-weld the cap to the container, saidseal head comprising the heating ring shaped along the shape of theflange portion, and the high frequency induction heating coil wound in aplurality of windings provided on the inside of the heating ring andheld between magnetic shielding plates, by heating the heating ringshaped along the shape of the flange portion with the high frequencyinduction heating coil held between the magnetic shielding plates, theheating ring can be heated concentrically to a temperature necessary forsealing the cap in a short period of time and, therefore, influence ofdropping in the temperature and inflation of gas in the head space canbe prevented and high-speed and stable sealing can be achieved with aseal head having a shape necessary for sealing of the cap.

In the fifteenth aspect of the invention, there is provided an apparatusfor heat-sealing a container as defined in the fourteenth aspect whereinthe heating ring of the seal head comprises a hollow portion which is acooling medium flow-path capable of cooling the heating ring while theheating ring is pressed on the cap and a plurality of cooling mediumsupplying and exhausting openings provided in the cooling mediumflow-path which can change a supplying and exhausting position of thecooling medium.

According to this apparatus for heat-sealing a container, the heatingring of the seal head comprises the hollow portion which is the coolingmedium flow-path capable of cooling the heating ring while the heatingring is pressed on the cap and a plurality of cooling medium supplyingand exhausting openings provided in the cooling medium flow-path whichcan change a supplying and exhausting position of the cooling medium. Bymaking the heating ring hollow and using the inside of the hollowportion as the cooling medium flow-path, and carrying out cooling whilechanging the supplying and exhausting position of the cooling mediumamong the plurality of cooling medium supplying and exhausting openings,adhering of the cap to the heating ring can be prevented and high-speedand stable sealing can be made even in a higher degree and, further,uniform cooling and uniform next heating can also be realized.

In the sixteenth aspect of the invention, there is provided an apparatusfor heat-sealing a container as defined in the fourteenth or fifteenthaspect claim wherein the heating ring comprises a non-welding member ona surface of the heating ring which presses the cap.

According to this apparatus for heat-sealing a container, since theheating ring comprises a non-welding member on a surface of the heatingring which presses the cap, even if the sealing temperature is raised,adhering of the cap to the heating ring can be prevented by covering ofthe heating ring and sealing at a high speed and in a stable manner canbe achieved even in a higher degree.

In the seventeenth aspect of the invention, there is provided anapparatus for heat-sealing a container as defined in the fifteenth orsixteenth aspect wherein the heating ring comprises cooling mediumexhausting means for exhausting the cooling medium in the cooling mediumflow-path after cooling of the cap.

According to this apparatus for heat-sealing a container, since theheating ring comprises cooling medium exhausting means for exhaustingthe cooling medium in the cooling medium flow-path after cooling of thecap, heating for sealing a next cap can be made in an even shorterperiod of time and sealing can be made at a high speed and in a stablemanner.

In the eighteenth aspect of the invention, there is provided anapparatus for heat-sealing a container as defined in any of thefourteenth-seventeenth aspects wherein the seal head comprisestemperature holding means for holding heating temperature of the heatingring.

According to this apparatus for heat-sealing a container, since the sealhead comprises temperature holding means for holding heating temperatureof the heating ring, a temperature which becomes a basis of temperaturerange of heating and cooling can be maintained and, therefore, whenheating and cooling are repeated, sealing can be made at a high speedand in a stable manner in an even shorter period of time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view showing a container used in an embodiment ofthe container heat-sealing method and apparatus of the presentinvention.

FIG. 2 a vertical section showing an embodiment of the containerheat-sealing method and apparatus of the present invention.

FIG. 3 is a schematic plan view showing an embodiment in which thecontainer heat-sealing method and apparatus of the invention are appliedto a rotary type heat-sealing apparatus carrying out high speedcontinuous heat-sealing.

FIG. 4 is a schematic view of another embodiment of the containerheat-sealing method and apparatus of the present invention.

FIG. 5 is a schematic vertical section of the embodiment shown in FIG.4.

FIG. 6A is an explanatory view of heating and cooling processes of anembodiment of the container heat-sealing method and apparatus and FIG.6B is an explanatory view of change in temperature of this embodiment.

FIG. 7A is a schematic view of the prior art heat-sealing apparatus andFIG. 7B is a cross sectional view of this apparatus.

FIG. 8 is a sectional view showing another example of the heating ringof the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Description will now be made in detail about embodiments of the presentinvention with reference to the accompanying drawings.

FIGS. 1 and 2 show an embodiment of the container heat-sealing methodand apparatus. FIG. 1 is an exploded view of the container and FIG. 2 isa vertical sectional view of the embodiment of the heat-sealingapparatus.

In this container heat-sealing apparatus (hereinafter referred simply toas “heat-sealing apparatus”) 20, as shown in FIG. 1, a container 10 iscomposed of a container main body 11 and a cap 12 which covers thecontainer main body 11. This container main body 11 is formed in theshape of a cup and has, in the periphery of an upper end openingportion, a flange portion 11 a which extends horizontally outwardly. Thecap 12 has, in its outer peripheral portion, a heat seal portion 12 awhich extends horizontally corresponding to the flange portion 11 a.This annular heat seal portion 12 a is formed integrally on the innerside thereof with a recessed cap portion 12 b which projects downwardlyto be positioned in the container. As the cap 12, a normal flat platetype cap including the heat seal portion 12 a and is not formed in theshape of a recessed cap portion may also be used.

The heat-sealing apparatus 20 which heat-seals the container main body11 and the cap 12 together has, as shown in FIG. 2, a seal head 21.

A seal head main body 22 of the seal head 21 is provided with a heatwelding member 23 having the same shape as and corresponding to theshape of the heat seal portion 12 a of the cap 12, for example, a hollowring shape, in such a manner that the lower surface of the heat weldingmember 23 is exposed. The hollow portion 23 a of the heat welding member23 constitutes a flow-path of a cooling medium, e.g., cooling water anda cooling medium pipe 24 is connected to the flow-path to supply andexhaust the cooling medium.

This heat welding member 23 is made of a material, e.g., metal, whichcan be heated by high frequency induction heating.

A high frequency heating coil 25 is disposed above the heat weldingmember 23 of the seal head main body 22 of the seal head 21. The coil 25has windings of, e.g., three windings in a horizontal plane parallel tothe upper surface of the heat welding member 23 and is connected to ahigh frequency power source through an electric current supply member(feeder) 26 connected to one end portion of the coil 25. This highfrequency heating coil 25 is also made hollow and a cooling medium suchas cooling water can be supplied to and exhausted from this hollowportion via a cooling medium pipe 27.

A ferromagnetic substance member 28 is provided in the seal head mainbody 22 in a manner to surround the heat welding member 23 and the highfrequency heating coil 25. The seal head 21 thus composed can be movedvertically and moved for pressing by means of an unillustrated elevatingand pressing device.

In this heat-sealing apparatus 20, a container support 29 is providedbelow the seal head 21 to support the lower surface of the flangeportion 11 a of the container main body 11.

The cap 12 is placed on the container main body 11 which is supported bythe container support 29 and is filled with contents and, after the heatseal portion 12 a of the cap 12 is superposed on the flange portion 11 aof the container main body 11, the cap 12 is pressed between thecontainer support 29 and the seal head 21.

Description will now be made about the operation of the heat-sealingapparatus 20 having the above described structure as well as the methodfor heat-sealing a container.

This type of heat-sealing apparatus 20 is normally provided on a fillingline of the container 10 and is used for high speed continuousproduction according to which contents are filled in the container mainbody 11 and then the cap 12 is placed on the container main body 11 andsealed by heat-sealing. Description will however be made with respect toan example in which a single container is heat-sealed.

After contents are filled in the container main body 11 of which theflange portion 11 a is supported by the container support 29, the cap 12is placed on the container main body 11 and the heat seal portion 12 aof the cap 12 is superposed on the flange portion 11 a of the containermain body 11 with the recessed cap portion 12 b projecting into the headspace of the container main body 11 thereby reducing the capacity of thehead space. In a case where a normal flat type cap having no recessedcap portion is used as the cap, the cap 12 is placed on the containermain body 11 in such a manner that the heat seal portion 12 a issuperposed on the flange portion 11 a.

In the seal head 21, in parallel to mounting of the cap 12, highfrequency current is supplied from the high frequency current source tothe high frequency heating coil 25 through the electric current supplymember 26 to heat the surface of the heat welding member 23. Thisheating by the high frequency heating coil 25 is high frequencyinduction heating according to which high frequency flux generated byhigh frequency current penetrates the heat welding member 23 which isthe object of heating and thereby induces an eddy current having a veryhigh density which heats the surface of the heat welding member 23.

The temperature of heating of this seal head 21 will suffice if thecontainer main body 11 and the cap 12 which constitute the container 10to be welded by heat-sealing are welded and sealed together. Temperaturecontrol is made by determining the temperature of heating at a propervalue depending upon the materials of the container main body 11 and thecap 12. By way of example, in a case where the cap is made ofpolyethylene terephthalate resin or a case where the cap is made ofstacked layers and polypropylene resin is used as an inner sealantmaterial, temperature required for heat-sealing usually is within arange from 180° C. to 220° C.

The seal head 21 which has been heated to a temperature required forheat-sealing is moved by the unillustrated elevating and pressing deviceto press the heat seal portion 12 a of the cap 12 to the flange portion11 a of the container main body 11 which is supported by the containersupport 29 with the cap 12 placed thereon.

Since the heated heat welding member 23 of the seal had 21 has the sameshape as the shape of the flange portion 11 a and the heat seal portion12 a, a portion which is necessary for heat-sealing only is heated andpressed and heat-sealing is made at a predetermined temperature.

In the heating by this seal head 21, the central portion (the recessedportion 12 b) of the cap 12 is not directly heated by virtue of theshape of the heat welding member 23 and the shape of the cap 12 havingthe recessed portion 12 b but the flange portion 11 a and the heat sealportion 12 a only are directly heated and, therefore, even heat-sealingis made at a high temperature, inflation of gas in the head space of thecontainer main body 11 can be held to the minimum and expansion of thecap 12 can also be prevented so that failure in sealing due to thesecauses can be prevented. Even if the cap 12 is formed in a flat plateshape, direct heating of its central portion can be prevented.

Then, cooling water as the cooling medium is supplied to the hollowportion 23 a of the heat welding member 23 of the seal head 21 throughthe cooling medium pipe 24 for cooling the heat welding member 23compulsorily while the heat welding member 23 is kept pressed to theheat seal portion 12 a of the cap 12. The seal head 21 then is elevatedby the elevating and pressing device and heat-sealing of one container10 is thus completed.

Since pressing is finished after the heat welding member 23 is cooled inthe above described manner, even if the heat-sealing is made at a hightemperature, adhering of the cap 12 (i.e., a covering material of thecap such as a heat-sealing film) to the surface of the heat weldingmember 23 can be prevented and, therefore, high speed and stableheat-sealing can be achieved. Accordingly, materials which have beensaid to have difficulty in heat welding such as polyester resins e.g.,polyethylene terephthalate and polyethylene naphthalate and polyamideresins e.g., nylon can be used for heat-sealing whereby the scope ofmaterials to which heat-sealing is applicable can be broadened.

By forming a cover layer 30 made of a material which can prevent heatwelding of the heat seal portion 12 a of the cap 12, e.g., fluorinecontaining resin or polyimide on the surface of the heat welding member23 which contacts the heat seal portion 12 a of the cap 12, adhering ofthe cap 12 can be completely prevented.

For preparing for heat-sealing of a next container, cooling mediumexhausting means 31 may be provided for exhausting the cooling mediumwhich was supplied to the hollow portion 23 a of the heat welding member23 so that next heating may be made easily and in a short period oftime. As this cooling medium exhausting means 31, for example, achangeover valve 32 may be provided in the cooling medium pipe 24 toenable supply of a fluid 33, e.g., compressed air, which has a smallerheat capacity than the cooling medium so that the cooling medium may bereplaced by air simultaneously with exhaustion and recovery of thecooling medium from the hollow portion 23 a of the heat welding member23.

By replacing the cooling medium in the hollow portion 23 a of the heatwelding member 23 by air having a smaller heat capacity than the coolingmedium such as cooling water, heating time can be shortened andheat-sealing thereby can be made at a higher speed.

For shortening heating time until next heat-sealing after cooling of theseal head 21, an electric heater 34 which constitutes the temperatureholding means may be provided adjacent to the heat welding member 23 ofthe seal head 22 and temperature may be controlled so that, aftertemperature is lowered to a value at which adhering of the cap 12 can beprevented, the temperature will not be lowered further so that atemperature which becomes a basis of temperature range of heating andcooling, i.e., the lowest temperature in the temperature range, can bemaintained.

By this arrangement, even when high frequency induction heating of theheat welding member 23 of the seal head 21 is made with the highfrequency heating coil 25, temperature is maintained at the lowesttemperature required for heat-sealing by the electric heater 34 or thelike constituting the temperature holding means and, therefore, heatingmay be made on the basis of this lowest temperature in the temperaturerange, i.e., heating starting temperature whereby the heat weldingmember 23 can be heated to the heat-sealing temperature in a shorterperiod of time.

In a case where high-speed continuous heat-sealing is made by using suchheat-sealing apparatus 20, a rotary type heat-sealing apparatus 40(hereinafter referred simply to as “heat-sealing apparatus 40) as shownin the schematic plan view of FIG. 3, for example, is used.

In this heat-sealing apparatus 40, a container main body supply unit Aof a rotary type container main body conveying apparatus 41 whichconveys the container main body 11 filled with contents conveys thecontainer main body 11 to a cap supply position B while replacing thehead space of the container main body 11 with inert gas or other gas. Atthis cap supply position B, the cap 12 which is conveyed from a capstack position C by a cap conveying apparatus 42 is placed on thecontainer main body 11 and the container main body 11 then is conveyedto a heating position D of the container main body conveying apparatus41 by moving in a rotating locus.

At this heating position D, the seal head 21 which is induction heatedby the high frequency induction coil 25 is lowered to press and heat theheat seal portion 12 a of the cap 12 and conveys the container main body11 to a cooling position E in a rotating locus while maintaining thispressing state.

At the cooling position E, cooling water is supplied as the coolingmedium from the cooling medium pipe 24 to the hollow portion 23 a of theheat welding member 23 to start cooling. Then, at a container dischargeposition F, the seal head 21 is elevated and the sealed container 10 isdischarged.

Thus, heat-sealing of one container is completed in the rotary conveyingof the container from the cap supply position B to the containerdischarge position F. Then, in the course of return movement from thecontainer discharge position F to the heating position D, discharge ofthe cooling medium and high frequency induction heating necessary fornext heat-sealing are made at a position such as position G.

According to the heat-sealing apparatus 40 combined with the rotary typeconveying apparatus, heat-sealing can be finished by cooling while theseal head is maintained in a pressing state and, therefore, heat-sealingcan be made continuously at a high speed. For example, according to thisheat-sealing apparatus 40, high speed sealing of 600 containers perminute can be realized in contrast to the prior art apparatus in whichheat-sealing speed is 20 to 30 containers per minute.

FIG. 4 is a schematic view of another embodiment of the invention andFIG. 5 is a schematic vertical section of the embodiment of FIG. 4.

A heat-sealing apparatus 20 for carrying out heat-sealing comprises, asshown in FIGS. 4 and 5, a seal head 122 which is mounted on the lowersurface of an upper portion of an apparatus frame 121.

This seal head 122 comprises a seal head main body 123 which is composedof a cylindrical central member 123 a and an outer annular member 123 b.The central member 123 a and the annular member 123 b are attachedconcentrically to the apparatus frame 121 and an annular opening 123 cbetween the central member 123 a and the annular member 123 bconstitutes an annular opening corresponding to the shape of the heatseal portion 12 a of the cap 12 which has the same shape as the flangeportion 11 a of the container 10.

In the annular opening 12 c of the seal head 123, there is provided aheating ring 124 shaped along the heat seal portion 12 a which is thesame as shape of the flange portion 11 a of the container main body 11.

The heating ring 124 is shaped in the form of a ring having a generallyU-shaped section which opens upwardly and having outwardly extendingflange portions 124 a at both inner and outer circumferences in theupper portion. The flange portions 124 a are in abutting engagement withstepped portions formed in the lower portions of the seal head main body123. A bottom portion 124 b of the heating ring 124 is exposed in thelower surface thereof to the space below and held between a supportplate 123 d in the shape of a disk and a support plate 123 e in theshape of a ring. By this arrangement, an annular space is formed withthe apparatus frame 121, the seal head main body 123 and the heatingring 124.

The bottom portion 124 b of the heating ring 124 is made hollow to forma hollow portion 124 c which constitutes a flow-path of a cooling mediumsuch as cooling water. A plurality of cooling medium supplying andexhausting openings 124 d are formed to communicate with the flow-path.In the illustrated example, two opening 124 d are formed at diagonalpositions and these openings 124 d are respectively connected to coolingmedium pipes 125 so hat the cooling medium can be supplied and exhaustedfrom either of these pipes 125.

The heating ring 124 is made of a material, e.g., metal, which can beheated by high frequency induction heating.

In the annular space between the seal head main body 123 and the heatingring 124 of the seal head 122, a high frequency induction heating coil126 is disposed in such a manner that it is held on both sides thereofbetween magnetic shielding plates 127. This high frequency inductionheating coil 126 is wound, for example, in plural windings in bothhorizontal and vertical directions and is connected to a high frequencyoscillator 128 via an electricity supply member (feeder) 128 a providedat the end of the coil 126. This high frequency induction heating coil126 is made hollow to form a hollow portion and the cooling medium suchas cooling water can be supplied to and exhausted from this hollowportion through an unillustrated cooling medium pipe.

Opposing the seal head 122, a container support 129 is provided in thelower portion of the apparatus frame 121 to support the lower surface ofthe flange portion 11 a of the container main body 11 of the container10.

In this heat-sealing apparatus 20, an elevating and pressing device 130is provided so that, after the cap 12 is placed on the container mainbody 11 which is supported by the container support 129 and filled withcontents in such a manner that the heat seal portion 12 a of the cap 12is superposed on the flange portion 11 a of the container main body 11,these portions can be pressed between the container support 129 and theseal head 122.

To this elevating and pressing device 130 is attached the containersupport through an air cylinder 131. By elevating the container support129 and further stretching the rod, the heat seal portion 12 a of thecap 12 superposed on the flange portion 11 a of the container main body11 is pressed between the container support 129 and the seal head 122.

Pressing of the heat-sealing portion 12 a of the cap 12 superposed onthe flange portion 11 a of the container 11 may be made not only byvertically moving the container support 129 but also by verticallymoving the seal head 122.

Description will now be made about the operation of the heat-sealingapparatus 20 constructed in the above described manner as well as themethod for heat-sealing the container.

This type of heat-sealing apparatus 20 is normally provided on a fillingline of the container 10 and is used for high speed continuousproduction according to which contents are filled in the container mainbody 11 and then the cap 12 is placed on the container main body 11 andsealed by heat-sealing. Description will however be made with respect toan example in which a single container is heat-sealed.

After contents are filled in the container main body 11 of which theflange portion 11 a is supported by the container support 129, the cap12 is placed on the container main body 11 and the heat seal portion 12a of the cap 12 is superposed on the flange portion 11 a of thecontainer main body 11 with the recessed cap portion 12 b projectinginto the head space of the container main body 11 thereby reducing thecapacity of the head space. In a case where a normal flat type caphaving no recessed cap portion is used as the cap, the cap 12 is placedon the container main body 11 in such a manner that the heat sealportion 12 a is superposed on the flange portion 11 a as shown in FIGS.4 and 5.

In the seal head 122, in parallel to mounting of the cap 12, highfrequency current is supplied from the high frequency oscillator 128 tothe high frequency induction heating coil 126 through the electriccurrent supply member 128 a to heat the surface of the bottom portion124 b of the heating ring 124. This heating by the high frequencyinduction heating coil 126 is high frequency induction heating accordingto which high frequency flux generated by high frequency currentpenetrates the heating ring 124 which is the object of heating andthereby induces an eddy current having a very high density which heatsthe surface of the bottom portion 124 b of the heating ring 124.

The temperature of heating of this heating ring 124 of the seal head 122will suffice if the container main body 11 and the cap 12 whichconstitute the container 10 to be welded by heat-sealing are welded andsealed together. Temperature control is made by determining thetemperature of heating at a proper value depending upon the materials ofthe container main body 11 and the cap 12. By way of example, in a casewhere the cap is made of polyethylene terephthalate resin or a casewhere the cap is made of stacked layers and polypropylene resin is usedas an inner sealant material, temperature required for heat-sealingusually is within a range from 180° C. to 220° C.

Then, by operating the air cylinder 131 of the elevating and pressingdevice 130, the container main body 11 which is supported by thecontainer support and is covered with the cap 12 with the heat sealportion 12 a of the cap 12 being superposed on the flange portion 11 aof the container main body 11 is elevated and pressed to the seal head122 in which the heating ring 124 has been heated to a temperaturenecessary for heat-sealing.

Since the heating ring 124 of the seal head 122 is formed along (i.e.,in the same shape as) the shape of the flange portion 11 a and the heatseal portion 12 a, heat-sealing is performed at a predeterminedtemperature with the portion necessary for heat-sealing only beingheated and pressed.

The heating and cooling processes by the heat-sealing apparatus 20 andtemperature change in these processes are shown in FIGS. 6A and 6B. Asshown in these figures, the heating ring 124 is heated to apredetermined temperature, e.g., 180° C. and then heating by the highfrequency oscillator 128 is stopped and pressing by the elevating andpressing device 120 only is maintained.

In the heating by this seal head 122, the central portion (the recessedportion 12 b) of the cap 12 is not directly heated by virtue of theshape of the heating ring 124 and the shape of the cap 12 having therecessed portion 12 b but the flange portion 11 a and the heat sealportion 12 a only are directly heated and, therefore, even ifheat-sealing is made at a high temperature, inflation of gas in the headspace of the container main body 11 can be held to the minimum andexpansion of the cap 12 can also be prevented so that failure in sealingdue to these causes can be prevented. Even if the cap 12 is formed in aflat plate shape as shown in FIGS. 4 and 5, direct heating of itscentral portion can be prevented.

Since the heating ring 124 is formed in the annular shape having theU-shaped section, the heating ring 124 is thin and has a small heatcapacity and therefore can be heated to a high temperature in ashort-period of time with the high frequency induction coil 126 havingplural windings in the horizontal and vertical directions. Moreover,drop in the temperature after stopping supply of electric current isrelatively small and a predetermined temperature can be maintainedwhereby sealing can be achieved by maintaining pressing with the heatingring 124 for a period of time necessary for heat-sealing.

After heat welding by the heating ring 124 of the seal head 122 is madeby maintaining pressing of the heating ring 124, cooling water as thecooling medium is supplied through the cooling medium pipe 125 to thecooling medium flow-path formed by the hollow portion 124 c of theheating ring 124 with one of the cooling medium supplying and exhaustingopenings 124 d being used as a supplying opening and another of theopenings 124 d being used as an exhausting opening to compulsorily coolthe heating ring 124. After the heating ring 124 is cooled to apredetermined temperature, the container support 129 is lowered by theelevating and pressing device 130 to complete heat-sealing of onecontainer 10. Cooling of the heating ring 124 to a predeterminedtemperature is continued even after lowering of the container 10 anddischarge of water (see FIG. 6A) to be described later is performed.

By this arrangement, since pressing is finished while the heating ring124 of the seal head 122 is cooled, even if heating time is shortened byelevating the heating temperature, adhering of the cap 12 (i.e., thecovering material of the cap such as a heat-sealing film) to the surfaceof the heating ring 124 of the seal head 122 can be prevented wherebyhigh-speed and stable heat-sealing can be achieved. Besides, since theheating ring 124 is formed annularly and thin, it has a small heatcapacity and therefore can be cooled in a short period of time.

FIG. 8 shows a modified example of the heating ring.

In the heating ring 224 of FIG. 8, the same component elements as thoseof the heating ring shown in FIG. 5 are designated by the same referencecharacters and description thereof will be omitted.

This heating ring 224 is divided in two portions of the upper portionand the lower portion. The upper portion 224 a is formed integrally witha central portion 123 a and is made of a synthetic resin, e.g.,polyether ether ketone resin and the lower portion 224 b is made ofmetal. A cooling medium is supplied to an opening portion 226 betweenthe upper portion 224 a and the lower portion 224 b. A gap between theupper portion 224 a and the lower portion 224 b is sealed with an O-ring227. Reference character 228 designates a blank plug and referencecharacter 229 designates a heating ring holder.

According to such heat-sealing apparatus 20, materials which have beensaid to have difficulty in heat welding such as polyester resins e.g.,polyethylene terephthalate and polyethylene naphthalate and polyamideresins e.g., nylon which have a relatively high melting point can beused as the cap for heat-sealing whereby the scope of materials to whichheat-sealing is applicable can be broadened. Additionally, thickness ofthe cap can be increased to such a degree that the invention isapplicable to a cap formed by injection molding. Even in a case wherethe material of the cap is changed in the above described manner, bymaintaining pressing of the heating ring 124 for a period of time afterheating the heating ring 124 to a predetermined temperature until startof the cooling process with supply of electric current being stopped,temperature and time necessary for heat welding the material can besecured.

By forming, as shown in the enlarged view of FIG. 5, a cover layer 124 ewhich is made of a material such as fluoride resin or polyimide whichcan prevent heat welding of the heat seal portion 12 a of the cap 12 atleast on the surface of heating ring 124 which contacts the heat sealportion 12 a of the cap 12, adhering of the cap 12 can be completelyprevented.

For preparing for next heat-sealing of a container, the cooling mediumwhich has been supplied to the hollow portion 124 c of the heating ring124 may be discharged by providing an unillustrated cooling mediumexhausting means whereby discharge of water can be made in a simplemanner so that heating of the cooling water in the hollow portion 124 cin next heat-sealing will be obviated and heating of the heating ring124 can be made easily and in a short period of time.

As this cooling medium exhausting means, for example, a changeover valvemay be provided in the cooling medium pipe 125 to enable supply of afluid such as compressed air which has a smaller heat capacity than thecooling medium so that air can replace the cooling medium while thecooling medium is discharged and recovered from the hollow portion 124 cof the heating ring 124.

According to this arrangement, by replacing the cooling medium in thehollow portion 123 a of the heat welding member 123 with air which has asmaller heat capacity than the cooling water used as the cooling medium,heating time can be shortened and high speed heat-sealing thereby can berealized.

For further shortening heating time until next heat-sealing aftercooling of the seal head 122, an electric heater which constitutes thetemperature holding means may be provided adjacent to the heat weldingmember 124 of the seal head 122 and temperature may be controlled sothat, after temperature is lowered to a value at which adhering of thecap 12 can be prevented, the temperature will not be lowered further sothat a temperature which becomes a basis of temperature range of heatingand cooling, i.e., the lowest temperature in the temperature range, canbe maintained.

By this arrangement, even when high frequency induction heating of theheat welding member 124 of the seal head 122 is made with the highfrequency induction heating coil 126, temperature is maintained at thelowest temperature required for heat-sealing by the electric heater orthe like constituting the temperature holding means and, therefore,heating may be made on the basis of this lowest temperature in thetemperature range, i.e., heating starting time whereby the heat weldingmember 124 can be heated to the heat-sealing temperature in a shorterperiod of time.

Further, by supplying and exhausting the cooling medium throughdifferent ones of cooling medium supplying and exhausting openings 124 dwhen the heating ring 124 is cooled after finishing heat-sealing of anext container, drop of temperature in the portion of the heating ring124 where the cooling medium enters and elevation of temperature in theportion of the heating ring 124 where the cooling medium exits can beprevented whereby uniform cooling can be ensured notwithstandingrepeated heating and cooling. By this arrangement, temperature of theheating ring 124 by subsequent heating can be made uniform wherebyheat-sealing can be made with a stable quality.

In the above described embodiment, two cooling medium supplying andexhausting openings 124 d are diagonally provided and cooling is made bychanging the cooling medium supplying opening and the cooling mediumexhausting opening alternately each time the container 10 is changed.Alternatively, more than two cooling medium supplying and exhaustingopenings may be provided and cooling may be made by changing the coolingmedium supplying opening and the cooling medium exhausting opening in apredetermined order, or detecting temperature in some portions of theheating ring 124 and supplying and exhausting the cooling medium at asuitable position randomly so that distribution in the temperature willnot be produced. Further alternatively, the cooling medium may besupplied simultaneously from plural positions and exhausted from pluralpositions or a single position or the cooling medium may be suppliedfrom a single position and exhausted from plural positions.

In the above described embodiments, description has been made withrespect to a case where the cap having a recessed cap portion or a flatcap portion is placed on the container main body having the shape of acup. The shapes of the cap and the container main body are not limitedto these shapes but other shapes such as a tray may be used as theshapes of the cap and the container main body.

In the above described embodiments, either the seal head or thecontainer support is moved vertically to heat-seal a container duringthe heat-sealing process of the container. In these embodiments, theother of the seal head and the container support which has beendescribed as moveing vertically in these embodiments may be movedvertically for heat-sealing.

Supply of the cooling medium may be omitted depending upon the materialof the cap or the conditions of heating. In this case, time for theentire heat-sealing process may be shortened or heating time may belengthened.

Since heat-sealing at a high speed can be made, drinks which have in thepast been filled in a metal can or a PET bottle may be filled in thecontainer used in the present invention and the container may be sealedat a high speed. Prepared food containing a solid food or viscous foodmay also be filled in the container used in the present invention andthe container may be sealed at a high speed.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a method and an apparatus forheat-sealing a container. Particularly, in the case of heat-sealing acap in the form of a film on a container main body in the form of a cupmade of paper or a synthetic resin, heat-sealing can be made at a highspeed in a stable manner.

1. A method for heat-sealing a container by sealing the container byheat welding a cap on a flange portion provided in an opening portion ofthe container comprising a step of high frequency induction heating aseal head formed in the shape of the flange portion of the container andpressing the cap with the heated seal head to weld the cap to thecontainer.
 2. A method for heat-sealing a container as defined in claim1 further comprising a step of cooling the seal head while the heatedseal head is pressing the cap.
 3. A method for heat-sealing a containeras defined in claim 2 wherein cooling of the seal head is made bysupplying a cooling medium into the seal head.
 4. A method forheat-sealing a container by sealing the container by heat welding a capon a flange portion provided in an opening portion of the container witha seal head comprising a heating ring formed along the shape of theflange portion and a high frequency induction heating coil provided onthe inside of the heating ring via magnetic shielding plates, saidmethod comprising a step of high frequency induction heating the heatingring with the high frequency induction heating coil and pressing the capwith the heating ring to weld the cap to the container.
 5. A method forheat-treating a container as defined in claim 4 wherein supply ofelectricity to the high frequency induction heating coil is stoppedafter the heating ring has been heated to a predetermined temperatureand then pressing with the heating ring is continued for a predeterminedperiod of time.
 6. A method for heat-treating a container as defined inclaim 4 wherein the heating ring is cooled while pressing with theheating ring is continued.
 7. A method for heat-sealing a container asdefined in claim 6 wherein the heating ring has a hollow portion andcooling of the heating ring is made by supplying a cooling medium intothe hollow portion.
 8. A method for heat-sealing a container as definedin claim 7 wherein cooling of the heating ring with the cooling mediumand supplying of the cooling medium are made by providing a plurality ofcooling medium supplying and exhausting openings in the hollow portionof the heating ring and supplying and exhausting the cooling medium froma different one of the supplying and exhausting openings in apredetermined order or at random.
 9. An apparatus for heat-sealing acontainer comprising a seal head for sealing the container by heatwelding a cap on a flange portion provided in an opening portion of thecontainer, said seal head comprising a seal head main body, a heatwelding member provided in the seal head main body and formed in theshape of the flange portion, and a high frequency induction heating coilprovided in the seal head main body for high frequency induction heatingthe heat welding member.
 10. An apparatus for heat-sealing a containeras defined in claim 9 wherein the heat welding member comprises acooling medium flow-path which enables the heat welding member to coolwhile pressing of the heat welding member on the cap is maintained. 11.An apparatus for heat-sealing a container as defined in claim 9 whereinthe heat welding member comprises a non-welding member on a surface ofthe heat welding member which presses the cap.
 12. An apparatus forheat-sealing a container as defined in claim 10 wherein the heat weldingmember comprises cooling medium exhausting means for exhausting thecooling medium in the cooling medium flow-path after cooling of the cap.13. An apparatus for heat-sealing a container as defined in claim 9wherein the seal head main body comprises temperature holding means forholding heating temperature of the heat welding member.
 14. An apparatusfor heat-sealing a container comprising a seal head and sealing thecontainer by heating the seal head and pressing a cap placed on a flangeportion of an opening portion of the container with the heated seal headto heat-weld the cap to the container, said seal head comprising aheating ring shaped along the shape of the flange portion, and a highfrequency induction heating coil wound in a plurality of windingsprovided on the inside of the heating ring and held between magneticshielding plates.
 15. An apparatus for heat-sealing a container asdefined in claim 14 wherein the heating ring of the seal head comprisesa hollow portion which is a cooling medium flow-path capable of coolingthe heating ring while the heating ring is pressed on the cap and aplurality of cooling medium supplying and exhausting openings providedin the cooling medium flow-path which can change a supplying andexhausting position of the cooling medium.
 16. An apparatus forheat-sealing a container as defined in claim 14 wherein the heating ringcomprises a non-welding member on a surface of the heating ring whichpresses the cap.
 17. An apparatus for heat-sealing a container asdefined in claim 15 wherein the heating ring comprises cooling mediumexhausting means for exhausting the cooling medium in the cooling mediumflow-path after cooling of the cap.
 18. An apparatus for heat-sealing acontainer as defined in claim 14 wherein the seal head comprisestemperature holding means for holding heating temperature of the heatingring.
 19. A method for heat-treating a container as defined in claim 5wherein the heating ring is cooled while pressing with the heating ringis continued.
 20. An apparatus for heat-sealing a container as definedin claim 10 wherein the heat welding member comprises a non-weldingmember on a surface of the heat welding member which presses the cap.21. An apparatus for heat-sealing a container as defined in claim 15wherein the heating ring comprises a non-welding member on a surface ofthe heating ring which presses the cap.